Should I Be Applying Lime This Fall?

One of the most important activities farmers must get done and do correctly to help maximize a crop’s yield potential is the application of lime. When soil pH becomes too low for plants to access critical nutrients needed for growth and development, agricultural lime helps restore nutrient access.

Why is lime so important you ask? Think of it this way: you’ve worked up a real appetite and you are sitting at a table surrounded by plates of food, but you can only eat what is within reach. Maybe that slice of pizza you’ve been craving is just a couple of inches past your fingertips. But a huge fresh salad is parked right in front of you! Sure, you like salad, but you want a big juicy steak and some potatoes to complete your meal, like right now!!

What does this have to do with applying lime? Everything, if you’re a crop!

Lime neutralizes soil acidity and adds calcium, a micronutrient essential to plant growth. Soil pH that is too low can make certain nutrients available in copious amounts but make other nutrients unavailable, or even toxic to plants.

A soil pH between 6.0 and 7.0 is generally the recommended range where plant nutrients are most available (Figure 1), but that can vary depending on the crop you are growing.1

-If the pH is 5, about 54% of applied fertilizer may be unavailable to plants
-If the pH is 5.5, about 33% of applied fertilizer may be unavailable to plants
-If the pH is 6.0, about 20% of applied fertilizer may be unavailable to plants
-If the pH is 7.0, about 0% of applied fertilizer should be unavailable to plants

Alltext Figure 1. Nutrient availability based on soil pH. Image courtesy of Dr. Emerson Nafziger, University of Illinois.

The problem with lime is that it takes time to dissolve and its effects are not usually immediate. Lime should be applied about 3 to 6 months before planting to allow time for it to dissolve and begin to increase soil pH. It should be applied at least one month prior to any fertilizer applications since it can interfere with the availability of other essential nutrients.

Applying lime in the fall is ideal because it provides plenty of time for it to be worked into the soil profile. As the lime dissolves, soil pH can increase, and some unavailable nutrients can become available before the next growing season. The best way to determine what is needed (or not) in terms of liming is to use a detailed soil analysis. Soil samples should be pulled immediately after a crop is harvested in the fall and sent to a reputable lab. The soil analysis should include measurement of calcium and magnesium and the percentage saturation of each in the soil. Soil sampling should be done every couple of years after lime is applied to evaluate pH balance.

Work with your agronomist or retailer to understand what type of lime would be best applied based on the crop, current soil pH, soil type, and other related factors.

Jeremy Miner

Agronomist

Sources:

1How does soil pH affect fertilizers and fertility. Cornell University Cooperative Extension of Suffolk County. Cornell University.

2Effects of pH, sodicity, and salinity on soil fertility. Salinity Management. University of California.  https://ucanr.edu/.

Web sites verified 7/2/2020.

Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.

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